Photosensitive motion-to-current transducers



M. SKLAROFF ETAL 3,254,225

PHOTOSENSITIVE MOTION-TO-CURRENT TRANSDUCERS 2 Sheets-Sheet 1 May 31, 1966 Filed March 26, 1962 MOTION Q |NPUT J 2o V OUTPUT CURRENT MOTION 24 CURRENT F G I 34 59 I EV PHOTOCELL MOTION INPUT 7 24 5? VANE I 58 METER MOVEMENT 6 34 n H q 22 I :46 POWER 48 AMPLIFIER l8 SUPPLY CURRENT OUTPUT 20 F I G 2 34 59 32 34 59 o v wig 2 w 2 26 38 42 32 YIIIIIZ-YIIIIA 0 FIG.3. FIG.4. FIG.5.

INVENTORS Morton Skloroff 8 George Revesz ATTORNEY May 31, 1966 M. SKLAROFF ETAL 3,254,225

PHQTOSENSITIVE MOTION'TO CURRENT TRANSDUCERS 2 Sheets-Sheet 2 7 Filed March 26, 1962 'IIIIIII,

FIG

INVENTORS Morton Skloroff 8 George Revesz FIG.8.

United States Patent Office Patented May 31, 1966 ing an electric output current proportional to a mechanical input motion and more particularly, to a motion-tocurrent transducer of the servo-follower type.

It is, therefore, an object of this invention to provide a motion-to-current transducer of the servo-follower type.

Another object of this invention is to provide a motionto-cur-rent transducer, wherein the motion sensing element comprises a photoelectric means.

Still another object of this invention is to provide a motion-to-current transducer of the servo-follower type having a cnrrent-to-motion feedback loop therein.

Still another object of this invention is to provide a motion-to-current transducer of the servo-follower type having a current-to-motion feedback loop therein, wherein the stability of individual components within the said loop does not aifect the stability of the system.

Yet another object of this invention is to provide a motion-to-current transducer of the servo-follower type wherein a photoelectric means is variably exposed to a light source in proportion to an input motion to control a current amplifier and provide an output current in response to the said input motion and a follow-up or feedback loop is energized in response to the said output current to cause the photoelectric meansto be shielded from the said light source to negate the efiect of the said input motion.

These and other objects of this invention will become more apparent with reference to the following specification and drawings which relate to several preferred embodiments of the invention.

In the drawings:

FIGURE 1 is a block diagram of the invention;

FIGURE 2 is a schematic, in partial block diagram, of the invention;

FIGURE 3 is a detail of one embodiment of the invention;

' FIGURE 4 is a detail of another embodiment of the invention;

FIGURES is a detail of another embodiment of the invention;

FIGURE 6 is a detail of still another embodiment of the invention;

FIGURE 7 is a detail of yet another embodiment of the invention; and

FIGURE 8 is a schematic diagram of the invention including the detail of FIGURE 7.

Referring in detail to the drawings, and more particularly to FIGURE 1, the motion-to-current transducer of the present invention is shown to comprise a servo-follower system 10. g

The servo-follower 10 comprises a first transducer 12 having a motion input 14 and a current output 16, the

said first transducer 12 being a motion-to-current transducer; a second or output transducer 18 of the current-tocurrent type having as its input the current output 16 of the first transducer and having a current output 20 which is also the current output for the entire servo system 10; and a third or feedback transducer 22 of the currentto-motion type having the current output 20 of the system 10 as its input and having a motion output 24, constrained to follow the motion input 14, connected as a second motion input to the first transducer 12.

- light source 59 and the photocell 38 are stationary is Referring now to FIGURE 2, the first motion input 14 to the first motion-to-current transducer 12 is shown as controlling a moving shutter 26 in the first transducer 12 com-prising a flat plate 28 having a rectangular opening 30 therein. The shutter 26 is interposed between a light source (not shown), energized via a pair of leads 32 and 34 by a power source 36, and a photocell 38. The current output lfi from the photocell 38 is fed through a pair of leads 40 and 42 to the input of a current amplifier comprising the second transducer 18 of the system 10.

One side of the current output 20 from the second transducer 18 comprises a direct lead 44. The other side of the current output 20 comprises a lead 46 connected from the amplifier 18 with one side of a meter coil or meter field winding 48, the coil 48 being connected at its other end via a lead 50 in series with the power source 36 and thence via a lead 52 back to the other side of the said current output 20. Thus, the current amplifier controls the amount of current through the meter coil 48 which can be supplied thereto by the power source 36.

The meter coil or field winding 48 comprises the cur rent input portion of the third or current-to-motion transducer 22 which is shown as comprising a meter movement including the meter coil 48 wound on a meter core 54 and a swinging vane 56 comprising the motion output 24 of the said third transducer. The vane 56 is of sufficient surface area to fully cover the opening 30 in the shutter 26 and thus mask same to prevent light from the light source (not shown) from impinging on the photocell. The vane 56 is mounted on the meter pointer 57, which in turn is mounted on the meter armature 58, immediately adjacent and parallel to the fiat plate 28 of the shutter 30 and is movable relative thereto in response to the magnitude and direction of the current through the meter coil 48.

Referring to FIGURE 3, the light source is shown as comprising a single bulb 59 connected across the leads 32 and 34 from the power source 36. In this embodi-- ment, the moving vane 56 islocated between the moving shutter 26 and the photocell 38. The photocell 38 and the light source 59 are stationary in this embodiment.

In the embodiment of FIGURE 4, the light source 59 may be mounted intergral with the fiat plate 28 of the shutter 26 in registry with' one side of the shutter opening 30 therein. The vane 56 is located between the other side of the shutter opening 30 and the photocell 38, the photocell 38 being stationary in this embodiment. The light source 59, being mounted integral with the. shutter 26, is thus made movable therewith.

The embodiment of FIGURE 5 is substantially the reverse of that shown in FIGURE 4, in that the photocell 38 is mounted integral with the fiat plate 28 of the shutter 26 in registry with one side of the shutter opening 36) therein and the light source 59 is made stationary.

In the embodiment of FIGURE 6, the moving shutter is eliminated and the motion input 14 acts directly on the return spring 60 of the meter 22 (FIGURE 2) at the free end 62 thereof. The spring 60 is thus biased by the motion input 14 about a central pivot 64, at which pivot the said spring 60 is connected to the meter pointer 57 comprising the supporting arm of the swinging vane 56 interposed between the light source 59 and the photocell 38. Thus, a much simplified structure wherein. both-the provided by this embodiment.

While the stability of the follow-up system is generally not aifected by component stability within the feedback loop, variation of photocell characteristics or the intensity of the light source as a result of ambient variations, supply voltage or aging will be adverse to system stability. This effect is compensated in the embodi ment'shown in FIGURE 7. The circuit shown comprises a preferred embodiment of the current-to-current transducer or amplifier 18. Instead of a single photocell 38, however, a second compensating photocell 68 is connected in series therewith across the input and power leads 40' and 42' of the amplifier 18. The active element of the current amplifier 18 comprises a transistor 70 having emitter, base and collector electrodes 72, 74 and 76, respectively. The base electrode 74 is directly connected to a node 78 comprising the central tap of a variable two-element voltage divider formed by the series connected photocells 38 and 68, the node 78being the common junction therebetween. The collector 76 is connected via a collector resistor 80 to one output terminal 44 while the line 40" is connected directly to the other output terminal 46. The emitter 72 is connected via an emitter resistor 82 to the line 42. It is to be noted that the input and power leads 40' and 42 of the amplifier 18 are similar in function to the leads 40 and 42 of FIGURE 2 although not identical thereto as regards their circuit connections.

A complete schematic of an embodiment of the invention including a compensating circuit similar to that of FIGURE 7 and the embodiment of FIGURE 3 is shown in FIGURE 8.

While the light source 59, the shutter 26, the motion input 14, the vane 56, the first photocell 38, the second or compensating photocell 68, the meter coil 48 and the current output terminals .20 all bear the same numerals as defined in the foregoing embodiments, the remaining elements of FIGURE 8 will bear new numerals.

Referring now in detail to FIGURE 8, Power is brought into the circuit via leads 84 and 86 from a source (not shown) to the primary 88 of a transformer 90, the transformer 90 having a secondary 92.

The light source 59 is energized directly from the primary circuit of the transformer 90 via leads 94 and 96 connected, respectively, from the leads 84 and 86 to opposite sides of the light source 59.

The remainder of the system is powered via the secondary 92 having a first common power lead 98 and a second common power lead 100 extending therefrom on opposite ends thereof. The first power lead 98 includes a halfwave rectifier 102 adjacent the secondary winding 92 and poled for current tlow into that end of the said winding. A smoothing capacitor 104 is provided in a shunt branch across the power leads 98 and 100 which engages the first lead 98 at a junction 106 on the off-side of the rectifier 102 with respect to the secondary 92.

The first power lead 98 extends from the said off-side of the rectifier 102 to one side 108 of the current output terminals 20. The second power lead 100 is connected through the emitter-collector circuit of a transistor current amplifier 110 (equivalent to the current-to-current transducer 18 of FIGURES 1 and 2) and the meter coil 48, in series with the saidemitter-collector circuit, to the other side 112 of the current output terminals 20.

The transistor amplifier 110 comprises a single transistor 114 having emitter, collector and base terminals 116, 118 and 120, respectively, with the emitter-collector circuit thereof comprising an emitter resistor 122 connected from the second power lead 100 to the emitter 116 and thence through the said collector 118 which is connected in series with the meter coil 48.

The first or sensor photocell 38 is shown (as in FIG- URE 3) in proper position with the shutter 26 and moving vane 56 to receive light variations therethrough from the light source 59. The sensor photocell 38 and the second or compensating photocell 68 are connected in series as a shunt branch between the first and second power leads 98' and 100, respectively, and form a variable two element voltage divider having a center node or tap 124.

The base electrode 120 of the transistor 114 in the current amplifier 110 is connected directly to the center node 124 of the said voltage divider and 'the collector Operation In general operation of the motion-to-current transducer system 10, referring to FIGURE 1, a motion input 14 is transduced to a proportional current output 16 by the motion-to-current transducer 12 and the current output 16 is amplified by the current-to-current transducer or current amplifier 18 to produce an output current at the current output terminals 20 proportional to the original input motion at the motion input 14. The motionto-current transducer system 10 is stabilized by a feedback motion generated by a current-to-motion transducer 22 which produces a motion output 24 acting to nullify the effect on the system of the motion input 14. Thus, a servo-follower action is achieved in the system 10 and the output current at the terminals 20 may be used for any desired control purpose dependent on the initial motion input 14.

Referring now to FIGURE 2, the motion input 14 is applied directly to the shutter 26 whereby more or less illumination from the light source (not shown) is permitted to pass through the shutter opening 30 and impinge upon the photocell 38. At this point in the operation, the swinging or moving vane 56 is stationary and is initially positioned to effectively close the shutter opening 30. The combination of the shutter 26 moving relative to the vane 56 and the light source 59 and photocell 38 controlled thereby comprise the first or motion-to-current' transducer 12 of the system. The resultant change in one or more of the electric parameters of the photocell 38 in response to the motion input 14 acting on the shutter 26 results in a current output 16 in the leads 40 and 42 proportional to the motion input 14. v

The current output is thus amplified in the current amplifier or current-to-current transducer 18 whereby a current output is produced at the output terminals 20 via lead-44 on one side and through lead 46, meter coil 48, lead 50, the power source 36 and lead 52 on the other.

The output current through the meter coil 48 of the meter or current-to-motion transducer 22 causes the vane 56 mounted on the meter pointer 57 and armature 58, which combination comprises the motion output 24, to follow the movement of the shutter as determined by the magnitude of the current output of the amplifier 18 to thereby progressively close the shutter opening 30 until the motion of the shutter 26 has been duplicated by the vane 56, thus causing the current output at the output terminals 20 to go to some predetermined quiescent level. Of course, as long as motion of the shutter 26 continues in response, for example, to a time varying motion input 14, the current output at 20 and the motion of the vane 56 will be constrained to follow the shutter movement both electrically and mechanically, respectively.

With respect to the operation of the embodiments of FIGURES 3, 4 and 5, in each embodiment the shutter 26 is moved in response to a motion input and the vane 56 is constrained to follow the movement of the shutter.

The embodiment of FIGURE 3, by having both a stationary light source 59 and stationary photocell 38, provides for simplicity of manufacture of a motion-to-current transducer system of the present invention. In this embodiment, however, a photocell of relatively large sensitive area is necessary to sufiiciently provide for the full range of shutter movement.

The embodiment of FIGURE 4, by having the light source 59 mounted on the shutter 26, provides a system wherein a small light source 59 and a small and simple I changes the zero set point of the meter spring 60 by moving the free end 62 thereof about the pivot point 64 and thus, causes the meter pointer 57 to move the vane 56, to expose the photocell 38 to the light source 59 in proportion to the motion input 14. The feedback through the meter coil 48 (FIGURE 2) will constrain the vane 56 to retrace its initial motion and tend to shield the photocell 38 from the light source 59. This embodiment achieves extreme and practical simplicity in that the need for a shutter is entirely obviated.

With respect to the embodiment of FIGURE 7, the photocell 38 varies in impedance with the position of the shutter and/ or vane, depending on which of the embodiments of FIGURES 3, 4, 5 and 6 are used therewith, while the impedance of the second or compensating photocell 68 varies with ambient light variations. Thus, the bias applied to the base 74 of the transistor 70 in the amplifier or current-to-current transducer 18 is a function of the motion input to the system and the ambient conditions. The potential appearing at the node 78 is therefore a function of two variables but is actually representative only ,of the motion input since the second or compensating photocell 68 completely nullifies the effect of ambient conditions on the first or sensor photocell 38.

The variation in bias at the node 78 varies the base bias and hence the emitter-to-collector impedance of the transistor 70 in proportion to the motion input to the system, whereby the current output at the terminals 44 and 46 is also regulated in proportion thereto.

In the more fully detailed schematic of FIGURE 8, the motion input 14 drives the shutter 26 to expose the sensor photocell 38 to the light source 59 via the shutter opening 30 and thereby vary the potential of the node 124 between the sensor photocell 38 and the compensating photocell 68.

The resulting variation in bias to the base 120 of the transistor 114 in the current-to-current transducer 110 varies the emitter-to-collector impedance characteristics of the said transistor 114 in proportion to the motion input 14 to thereby vary the current output of the amplifier 110 through the meter coil 48 to one side 112 of the current output 20 in proportion to the said motion input. Any suitable device to be controlled may be connected across the leads 108 and 112 of the current output 20 and thus be controlled as a proportionate function of the input motion 14.

The output current in the meter coil or field winding 48 initiates a motion feedback through the dotted line meter linkage 130 to thereby constrain the vane 56 to follow the motion of the shutter 26 as imparted thereto by the motion input 14. Several important advantages are achieved by use of the compensating photocell 68, as shown in FIGURES 7 and 8 in addition to ambient light compensation. Since the compensating cell 68 is of the same material as'the first or sensing photocell 38, temperature compensation is provided thereby. Since photocell resistance is a function of the applied voltage, line voltage, compensation is also provided.

As can be seen from the foregoing specification and drawings this invention provides a new and motion-tocurrent transducer of the servo-follower type having extremely good stability and being compensated for ambient conditions. This system produces currents at the'output thereof proportional to motions applied to the input for the purpose of effecting controls on and/or in response to the cause of the said input motion. Examples of motion inputs would be such things as Bourdon Tube expansion in response to pressure changes or liquid or gas filled bulbs expanding in response to temperature changes.

It is to be understood that the embodiments shown and described herein are -for the purpose of example only and are not intended to limit the scope of the appended claims.

What is claimed is:

1. A motion-to-current transducer system comprising a motion input means providing a motion input; a current output means providing a current output; a motion-tocurrent first transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion'third transducer connected at its input to said current output means and power source and wherein said photoelectric means com-' prises a sensor photocell controlled by said movable means and a compensating photocell continuously controlled in response to ambient conditions, said photocells being connected in series across said power source and having a common node therebetween comprising an output terminal of said first transducer.

2. The invention defined in claim 1, wherein said light source and said photoelectric means are maintained stationary.

3. The invention defined in claim 1, wherein said light source is mounted on one side of said shutter means for movement therewith in registry with said shutter means opening and said photoelectric means is maintained stationary adjacent the opposite side of said shutter means.

4. The invention defined in claim 1, wherein said photoelectric means is mounted on one side of said shutter means for movement therewith in registry with said shutter means opening and said light source is maintained stationary adjacent the opposite side of said shutter means.

5.-A motion-to-current transducer system comprising a motion input means providing a motion input; a current output means providing a current output; a motionto-current first transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to said current output means and at its output to the input of said first transducer to thereby provide a feedback motion relative to the said motion input as a function of the said current output of said current output means; said movable means comprising a shutter means, a shutter opening in said shutter, and a vane relatively movable with respect to said shutter means, the relative movement between said shutter means and said vane acting to vary the light transmitted from said light source to said photoelectric means through said shutter opening; and wherein said system includes a power source and wherein second transducer comprises a current amplifier including a transistor having base, collector and emitter terminals, said base terminal being connected to the output of said first transducer and the emitter-to-collector path of said transistor being connected across said power source and comprising the output circuit of said second transducer.

6. The invention defined in claim 5, wherein said light source and said photoelectric means are maintained stationary.

7. The invention defined in claim 5, wherein said light source is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said photoelectric means is maintained stationary adjacent the opposite side of said shutter means.

8. The invention defined in claim 5, wherein said photoelectric means is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said light source is maintained stationary adjacent the opposite side of said shutter means.

9. The invention defined in claim 5, wherein said photoelectric means comprises a sensor photocell controlled by said movable means and a compensating photocell continuously controlled in response to ambient conditions, said photocells being connected in series across said power source and having a common node therebetween comprising an output terminal of said first transducer.

10. A motion-to-current transducer system comprising a motion input meas providing a motion input; a current output means providing a current output; a motion-tocurrent first transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to said current output means and at its output to the input of said first transducer to thereby provide a feedback motion relative to the said motion input as a function of said current output of said current output means; said movable means comprising a shutter means, a shutter opening in said shutter means, and a vane relatively movable with respect to said shutter means, the relative movement between said shutter means and said vane acting to vary the light transmitted from said light source to said photoelectric means through said shutter opening; and wherein said third transducer comprises a driving means proportionally energized by said current output, means connecting said shutter means with said motion input means, and means connecting said vane of said movable means with said driving means whereby said vane is constrained by said driving means in response to said current output to follow the movement of said shutter means imparted thereto by said motion input means, whereby the light transmitted from said light source to said photoelectric means is varied 11. The invention defined in claim 10, wherein said system further includes a power source and wherein said photoelectric means comprises a sensor photocell controlled by said movable means and a compensating photocell continuously controlled in response to ambient conditions, said photocells being connected in series across said power source and having a common node therebetween comprising an output terminal of said first transducer.

12. The invention defined in claim 10, wherein said driving means comprises a current responsive meter movement including an armature and said means connecting said vane with said driving means comprises a supporting arm mounted on said armature and extending to said vane to thereby mount said vane for movement with said armature.

13. A motion-to-current transducer system comprising a motion input means providing a motion input; a current output means providing a current output; a motiona photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to said current output means and at its output to the input of said first transducer to thereby provide a feedback motion relative to the said motion input as a function of the said current output of said current output means; said movable means comprising a shutter means, a shutter opening in said shutter, and a vane relatively movable with respect to said shutter means, the relative movement between said shutter means and said vane acting to vary the light transmitted from said light source to said photoelectric means through said shutter opening; and wherein said second transducer comprises a current amplifier including a transistor having base, collector and emitter terminals, said base terminal being connected to the output of said first transducer and the emitter-to-collector path of said transistor being connected across said power source and comprising the output circuit of said second transducer; and wherein said third transducer comprises a driving means including a field winding connected in series with the said output circuit of said second transducer, whereby said driving means is proportionally energized in response to said current output and means connecting said driving means with said movable means.

14. The invention defined in claim 13, wherein said driving means further includes an armature and said means connecting said driving means with said movable means comprises means integral with said armature.

15. The invention defined in claim 10, wherein said light source and said photoelectric means are maintained stationary.

16. The invention defined in claim 10, wherein said light source is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said photoelectric means is maintained stationary adjacent the opposite side of said shutter means.

17. The invention defined in claim 10, wherein said photoelectric means is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said light source is maintained stationary adjacent the opposite side of said shutter means.

18. A motion-to-current transducer system comprising a power source, a motion input means providing a motion input, a current output means providing a current output, a motion-to-current first transducer connected with said motion input means and having an output, a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to said current output means and at its output to the input of said first transducer to thereby provide a feedback motion at said motion input means as a function of said current output; wherein said system includes a power source; wherein said first transducer comprises a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means and movable thereby to variably exposed said photoelectric means to said light source as a function of said motion input to thereby cause said photoelectric means to produce a variable output as a function of said motion input, said movable means comprising a shutter means, a shutter opening in said shutter, and 'a vane relatively movable with respect to said shutter means, the relative movement between said shutter means and said vane acting to vary the light transmitted from said light source to photoelectric means through said shutter opening, said shutter means being connected with said motion input means; wherein said second transducer comprises a current amplifier including a transistor having base, collector and emitter terminals, said base terminal being connected to the output of said first transducer and the emitter-to-collector path of said transistor being connected across said power source and comprising the output circuit of said second transducer; and wherein said third transducer comprises a driving means including a field winding connected in series with the said output circuit of said second transducer; whereby said driving means is proportionallyenergized in response to said current output, and means connecting said vane with said driving means whereby said vane is constrained by said driving means in response to said current-output to follow the movement of said shutter means imparted thereto by said motion input means. 19. The invention defined in claim 18, wherein said photoelectric means are maintained stationary.

20. The invention defined in claim 18, wherein said light source is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said photoelectric means is maintained stationary adjacent the opposite side of said shutter means.

21. The invention defined in claim 18, wherein said photoelectric means is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said light source is maintained stationary adjacent the opposite side of said shutter means.

22. The invention defined in'claim 18, wherein said photoelectric means comprises a sensor photocell controlled by said movable means and a compensating photocell continuously controlled in response to ambient conditions, said photocells being connected in series across said power source and having a common node therebetween comprising an output terminal of said first transducer.

23. The invention defined in claim 18, wherein said driving means further includes an armature and said means connecting said vane with said driving means comprises a supporting arm mounted on said armature and extending to said vane to thereby mount said vane for movement with said armature.

24. A motion-to-current transducer system comprising a motion input means providing a motion input; a current output means providing a current output; a motion-tocurrent first transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to said current output and at its output to the input of said first transducer to thereby provide a feedback motion at said motioninput means as a function of the current output of said current output means; said movable means comprising a vane, a sup-.

porting arm for said vane connected at one end to said vane and having a pivotal mounting at the other end, a resilient means connected at one of its ends to said other end of said arm and biasing said arm in a given direction about the said pivotal mounting, the other end of said resilient means being coupled with said motion input means; wherein said system further includes a power source and wherein said photoelectric means comprises a sensor photocell controlled by said movable means and a compensating photocell continuously controlled in response to ambient conditions, said photocells being connected in series across said power source and having a common node therebetween comprising an output terminal of said transducer.

25. A motion-to-current transducer system comprising a motion input means providing a motion input; a current output means providing a current output; a motion-to-current first transducer comprising a light source,

.a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second thereby provide a feedback motion relative to the said motion input as a function of the said current output of said current output means; said movable means comprising a shutter means, a shutter opening in said shutter, and a vane relatively movable with respect to said shutter means said shutter means and said vane being arranged to be connected one with said motion input means and onewith the said output of said third transducer means whereby one will respond to said motion input and the other will respond to said feedback motion, the relative movement between said shutter means and said vane acting to vary the light transmitted from said light source to photoelectric means through said shutter openmg. 7

26. The invention defined in claim 25, wherein said light source and said photoelectric means are maintained stationary.

27. A motion-to-current transducer system comprising a motion input means providing a motion input; a current output means providing a current output; a motionto-current first transducer comprising a light source, a photoelectric means and movable means between said light source'and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to' the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to said current output means and at its output to the input of said first trans- -means through said shutter opening; and wherein said light source is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said photoelectric means is maintained stationary adjacent the opposite side of said shutter means.

28. A motion-to-current transducer system comprising 1 a motion input means providing a motion input; a current output means providing a current output; a motionto-current first transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to saidcurrent output means and at its output to the input of said first transducer to thereby provide a feedback motion relative to the said motion input as a function of the said current output of said current output means; said movable means comprising a shutter means, a shutter opening in said shutter means, and

a vane relatively movable with respect to said shutter light source is maintained stationary adjacent the opposite side of said shutter means.

2 9. A motion-to-current transducer system comprising a motion input means providing a motion input; a current output means providing a current output; a motionto-current first transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with said motion input means; a current-to-current second transducer connected at its input to the output of said first transducer and having its output comprising said current output means, and a current-to-motion third transducer connected at its input to said current output means and at its output to the input of said first transducer to thereby provide a feedback motion at said motion input means as a function of said current outputof said current output means; wherein said third transducer comprises a driving means proportionally energized by said current output, said driving means comprising a current responsive meter movement including an armature, and means on said armature for connecting said driving means with said movable means; and wherein said movable means comprises a vane, 21 supporting arm for said vane connected at one end to said vane and having pivot means at the other end, and a resilient means connected at one of its ends to said other end of said arm and biasing said arm in a given direction about the pivot, the other end of said resilient means being coupled with said motion input means; and wherein said armature has an axis of rotation common with said pivot means on said supporting arm, and means on said armature for retaining said arm on said armature for motion there with about said pivot.

30. In a system of the class described including a light source, a motion-to-current transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with a motion input means providing a motion input, said movable means comprising a shutter means, a shutter opening in said shutter means, and a vane relatively movable with respect to said shutter means, the relative movement between said shutter means and said vane acting to vary the light transmitted from said light source to said photoelectric means through said shutter opening as a function of said motion input to thereby cause said photoelectric means to produce a variable output as a function of said motion input; wherein said light source is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said photoelectric means is maintained stationary adjacent the opposite side of said shutter means.

31. In a system of the class described including a light source, a motion-to-current transducer comprising a light source, a photoelectric means and movable means between said light source and said photoelectric means connected with a motion input means providing a motion input, said movable means comprising a shutter means, a shutter opening in said shutter means, and a vane rela tively movable with respect to said shutter means, the relative movement between said shutter means and said vane acting to vary the light transmitted from said light source to said photoelectric means through said shutter opening as a function of said motion input to thereby cause said photoelectric means to produce a variable output as a function of said motion input; wherein said photoelectric means is mounted on one side of said shutter means for movement therewith in registry with said shutter opening and said light source is maintained stationary adjacent the opposite said of said shutter means.

References Cited by the Examiner UNITED STATES PATENTS 1,523,149 1/1925 Wheeler 250231 X 2,141,175 12/1938 Dawson 250231 X 2,335,163 11/1943 Smith 250-231 X 2,978,954 4/1961 Watson 250-209 X 3,062,961 11/1962 Kalns et a1 250-209 X RALPH G. NILSON, Primary Examiner.

WALTER STOLWEIN, Examiner. 

1. A MOTION-TO-CURRENT TRANSDUCER SYSTEM COMPRISING A MOTION INPUT MEANS PROVIDING A MOTION INPUT; A CURRENT OUTPUT MEANS PROVIDING A CURRENT OUTPUT; A MOTION-TOCURRENT FIRST TRANSDUCER COMPRISING A LIGHT SOURCE, A PHOTOELECTRIC MEANS AND MOVABLE MEANS BETWEEN SAID LIGHT SOURCE AND SAID PHOTOELECTRIC MEANS CONNECTED WITH SAID MOTION INPUT MEANS; A CURRENT-TO-CURRENT SECOND TRANSDUCER CONNECTED AT ITS INPUT TO THE OUTPUT OF SAID FIRST TRANSDUCER AND HAVING ITS OUTPUT COMPRISING SAID CURRENT OUTPUT MEANS, AND A CURRENT-TO-MOTION THIRD TRANSDUCER CONNECTED AT ITS INPUT TO SAID CURRENT OUTPUT MEANS AND AT ITS OUTPUT TO THE INPUT OF SAID FIRST TRANSDUCER TO THEREBY PROVIDE A FEEDBACK MOTION RELATIVE TO THE SAID MOTION INPUT AS A FUNCTION OF THE SAME CURRENT OUTPUT OF SAID CURRENT OUTPUT MEANS; SAID MOVABLE MEANS COMPRISING A SHUTTER MEANS, A SHUTTER OPENING IN SAID SHUTTER MEANS, AND A VANE RELATIVELY MOVABLE WITH RESPECT TO SAID SHUTTER MEANS, THE RELATIVE MOVEMENT BETWEEN SAID SHUTTER MEANS AND SAID VANE ACTING TO VARY THE LIGHT TRANSMITTED FROM SAID LIGHT SOURCE TO SAID PHOTOELECTRIC MEANS THROUGH SAID SHUTTER OPENING; WHEREIN SAID SYSTEM FURTHER INCLUDES A POWER SOURCE AND WHEREIN SAID PHOTOELECTRIC MEANS COMPRISES A SENSOR PHOTOCELL CONTROLLED BY SAID MOVABLE MEANS AND A COMPENSATING PHOTOCELL CONTINUOUSLY CONTROLLED IN RESPONSE TO AMBIENT CONDITIONS, SAID PHOTOCELLS BEING CONNECTED IN SERIES ACROSS SAID POWER SOURCE AND HAVING A COMMON NODE THEREBETWEEN COMPRISING AN OUTPUT TERMINAL OF SAID FIRST TRANSDUCER. 